function $(id){return document.getElementById(id);}
window.onload = function (){


	/**按钮背景色的切换*/

	$("but1").addEventListener("click",function (){
		this.style.backgroundColor = "#B0B0B0";
		$("but2").style.backgroundColor="#C8C8C8";
		$("mid_1").className = "xian";
		$("mid_2").className = "yin";
	})
	$("but2").addEventListener("click",function (){
		this.style.backgroundColor = "#B0B0B0";
		$("but1").style.backgroundColor="#C8C8C8";
		$("mid_2").className = "xian";
		$("mid_1").className = "yin";
	})



}
